A direct-contact steam condenser is used for geothermal power generation and so on. Conventional direct-contact steam condensers include a tray type and a spray type, the latter being called a spray condenser. In both of these methods, since steam condensation takes place by the direct contact of turbine exhaust steam and cooling water, how an area of the cooling water in contact with the steam is increased is important in view of performance. In the tray type, the turbine exhaust steam flows perpendicularly to the cooling water dropping down from a perforated tray and by the use of its dynamic pressure, the cooling water is atomized. In the spray type, the cooling water is atomized when being discharged to space through spray nozzles. In the spray type, since the flow velocity of the turbine exhaust steam is not required for the atomization of the water, it is possible to reduce a flow loss of the steam in the steam condenser.
Further, since a large volume of the cooling water is processed in the direct-contact steam condenser, it is necessary to prevent the occurrence of what is called water induction (phenomenon that the cooling water collecting in the steam condenser flows back toward a steam turbine due to some reason to damage a brade in high-speed rotation). A method conventionally adopted to solve this problem is to install a steam turbine exhaust pipe on an upper side and lead exhaust steam into a steam condenser from above the steam condenser. In this method, consideration need to be given so that an upper space of the steam turbine has a large height, the steam turbine is installed at a high position, and the steam condenser is installed in a lower position, or the like, which gives a great influence not only on the equipment but also on construction cost.
A geothermal power plant utilizes steam extracted from the earth and, as a driving force of a steam turbine, uses a heat drop decided by a differential pressure to a pressure of a steam condenser, thereby generating power. The steam pressure when the steam is extracted from the earth varies depending on a site where the steam is extracted, but is generally about 5 kg·f/cm2 to about 8 kg·f/cm2, which is considerably lower than a main steam pressure of an ordinary thermal power plant. Further, since the geothermal power plant is generally installed in a district having a scarce cooling water resource, a method of recycling condensed steam as cooling water is adopted. Therefore, in many cases, the cooling water has a higher temperature than sea water and river water. In the steam condenser, even if it is a direct-contact type, the pressure cannot be made lower than a saturation pressure at the temperature of water produced after steam and cooling water are mixed, and therefore, it is important to reduce a flow loss of the steam when the steam flows from the steam turbine to the steam condenser. An effective method to achieve this is an axial flow exhaust method in which an exhaust direction of a steam turbine is set to an axial direction of the turbine that is a flow direction of the steam passing through a brade.
As described above, the steam condenser is generally of what is called a downflow type in which the exhaust steam flows downward from above the steam condenser to be led therein. In this type, a bend for changing the flow direction to the downward direction needs to be provided in an exhaust pipe, so that a flow loss occurs in the bend and a steam condenser needs to be installed at a lower position, which gives a great influence also on construction cost.